JP2007139632A - Reflectivity measuring instrument and reflectivity measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To arrange the detection intensity distribution of the whole by correcting quantity of light corresponding to the spectral characteristics of a device in a reflectivity measuring instrument. <P>SOLUTION: The reflectivity measuring instrument 1 is constituted so that the light from a light source device 3 is guided to a main body part 2 to be passed through a correction filter 5 and condensed to a lens W to be inspected to perform irradiation. Next, the reflected light from the surface W1 to be inspected of the lens W to be inspected is guided to a spectrometer 13 to be diffracted spectrally. Further, the correction filter 5 is constituted so that the spectral characteristics of the reflectivity measuring instrument 1 in case having no correction filter 5 are corrected and transmission characteristics are planned so that light of a wavelength region low in intensity is detected relatively easily. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reflectance measuring machine and a reflectance measuring method for measuring the reflectance of an optical component.

For a device that measures the reflectance of a lens or other test surface, the light beam from a white light source is folded back by a half mirror, collected by an objective lens, and irradiated to the test surface of the lens. Is configured to enter the light receiving element through a half mirror (see, for example, Patent Document 1). In this type of reflectance measuring machine, it is possible to measure the spectral reflectance by placing a spectroscope between the half mirror and the light receiving element and allowing the reflected light to enter the light receiving element while dispersing the reflected light. .
Japanese Examined Patent Publication No. 6-27706

However, the intensity of the light beam from the white light source is not constant at all wavelengths and often varies depending on the wavelength. Also in a lens system such as a condenser lens, the transmission intensity and reflection intensity of light for each wavelength differ depending on the characteristics of the antireflection film. For this reason, the intensity of the light beam incident on the light receiving element varies depending on the wavelength. Even if a light beam having a constant intensity at all wavelengths is incident on the light receiving element, the detection sensitivity of the light receiving element is different for each wavelength, so the intensity of light detected by the light receiving element is not constant. Therefore, the conventional reflectance measuring machine has spectral characteristics unique to the apparatus such that the detection intensity varies depending on the wavelength. If the spectral reflectance is measured when the change in detection intensity due to wavelength is large, a sufficient amount of light flux can be detected in the wavelength range where the detection intensity is high, but a sufficient amount of light flux is detected in the wavelength range where the detection intensity is low. Could not be detected. In this case, information that should originally be obtained cannot be obtained because it is buried in noise or the like, resulting in a problem that good measurement accuracy cannot be obtained. Note that if the light intensity, detection time, and detection sensitivity of the light receiving element are increased in accordance with the wavelength at which the detection intensity decreases, the detection value of the wavelength at which the detection intensity increases tends to saturate. Becomes difficult to obtain.
The present invention has been made in view of such circumstances, and its main purpose is to correct the distribution of the entire detection intensity by correcting the amount of light in accordance with the spectral characteristics of the apparatus.

The invention according to claim 1 of the present invention for solving the above-described problem is that a light beam from a white light source is incident on a test surface, and reflected light from the test surface is dispersed by a spectroscope and then received by a light receiving element. In the reflectance measuring machine that measures the reflectance of the test surface, the detection intensity of the light receiving element when the reflected light is detected by the light receiving element from the white light source to the test surface is measured. The reflectance measuring machine is characterized in that it is provided with a correcting means for reducing the variation depending on the wavelength.
This reflectance measuring machine uses a correction means that takes into account the spectral characteristics of the entire device when the intensity (detection intensity) of the light beam finally detected through the light receiving element varies greatly depending on the wavelength. To reduce variation.

According to a second aspect of the present invention, in the reflectance measuring instrument according to the first aspect, the correction unit cuts the light amount in the wavelength region where the detection intensity becomes high, and the output in the wavelength region where the detection intensity becomes low is detected. It is an optical filter that corrects the output to be 1% or more of the output of the region where the intensity is high.
In this reflectance measuring machine, among the light beams incident on the light receiving element, the light beam in the wavelength region where the detection intensity as a whole of the apparatus is high decreases in light amount, and the light beam in the wavelength region where the detection intensity decreases is relatively light. Become more.

According to a third aspect of the present invention, in the reflectance measuring machine according to the second aspect, the optical filter has a transmittance of 450 nm or less that is at least twice that of a transmittance near 700 nm.
This reflectance measurement apparatus corrects the detection intensity by increasing the amount of light on the short wavelength side and decreasing the amount of light on the long wavelength side.

According to a fourth aspect of the present invention, in the reflectance measuring machine according to the first aspect, the correction unit emits a light beam in a wavelength region where the detection intensity is low, and combines the light beam with the light beam from the white light source. It has the light source for compensation arranged in this way.
This reflectance measuring device corrects the detection intensity by increasing the light flux in the wavelength region where the detection intensity is low.

According to a fifth aspect of the present invention, the reflectance of the test surface is obtained by causing a light beam from a white light source to enter the test surface, separating the reflected light from the test surface with a spectroscope, and then receiving the light on a light receiving element. In the reflectance measurement method for measuring the light, the step of irradiating the surface to be measured after passing the light beam from the white light source through an optical filter and attenuating the amount of visible light having a wavelength of 500 nm or more; And reflecting the reflected light before the optical filter and entering the spectroscope.
In this reflectance measurement method, the amount of light on the short wavelength side is relatively increased by attenuating the amount of light in the wavelength region (500 nm or more) where the detection intensity on the short wavelength side is high as an apparatus-specific characteristic with an optical filter. . As a result, the intensity change for each wavelength of the light beam finally detected through the light receiving element is reduced.

  According to the present invention, the intensity of the light beam finally detected through the light receiving element is reduced by reducing the difference between the wavelength region where the detection intensity is low due to the spectral characteristics of the device and the wavelength region where the detection intensity is high. The distribution according to the wavelength can be adjusted. Therefore, the measurement accuracy in the reflectance measurement can be improved.

A first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of a reflectance measuring machine according to the present embodiment. The reflectance measuring device 1 is a device that measures the spectral reflectance of the lens surface, and includes a main body 2 and a light source device 3. The light source device 3 uses a white light source, for example, a halogen light source. The main body 2 and the light source device 3 are connected by a light guide 4 in which optical fibers are bundled in an annular shape. In the main body 2, a correction filter 5 that is correction means, a first pinhole plate 6, a first beam splitter 7, and an imaging lens are provided on the optical path of the annular light flux 3 a emitted from the light guide 4. 8 and the second beam splitter 9 are sequentially arranged at a predetermined interval. In the first pinhole plate 6, for example, a first pinhole 6A having a diameter of 0.2 mm is formed. The first beam splitter 7 is fixed with an inclination of 45 ° with respect to the optical axis of the light beam from the light guide 4. The imaging lens 8 collimates the light beam that has passed through the first beam splitter 7. The second beam splitter 9 is arranged at an angle of 45 ° parallel to the first beam splitter, and turns the light beam downward by 90 °.

  Further, an objective lens 10 is disposed below the second beam splitter 9, and a lens W to be inspected is disposed further below the objective lens 10. The imaging lens 8 and the objective lens 10 are designed so that an image of the first pinhole 6A is formed on the surface (test surface W1) of the test lens W.

An observation optical system 11 is installed above the second beam splitter 9 so that an enlarged image of the test lens W can be observed with light transmitted through the second beam splitter 9.
A second pinhole plate 12 and a spectrometer 13 are disposed above the first beam splitter 7. A second pinhole 12 </ b> A is formed in the second pinhole plate 12. The second pinhole 12A is disposed on the optical path of the light beam folded by the first beam splitter 7. The diameter of the second pinhole 12A is larger than that of the first pinhole 6A, and is, for example, 0.3 mm in diameter.

  In the spectroscope 13, the grating 14 is installed at a predetermined inclination angle on the optical path of the light beam passing through the second pinhole 12A. A mirror 15 is disposed on the optical path of the light beam reflected by the grating 14 at a different angle for each wavelength. The mirror 15 is arranged so that the folded light beam enters a predetermined position of the line sensor 16. The line sensor 16 has a configuration in which light receiving elements are arranged. The line sensor 16 is connected to the controller 18 via a signal line 17 so that a signal corresponding to the amount of light received by the light receiving element is output. The controller 18 includes a plurality of memories (memory M1, M2, M3,...) And an arithmetic device C. The arithmetic device C is configured to execute control processing based on the control of the exposure time of the line sensor 16 and the output of the line sensor 16.

  The correction filter 5 is determined by the characteristics of the light source device 3, the transmission characteristics of the optical system including the light guide 4, the reflection characteristics, the spectral characteristics of the grating 14, the detection sensitivity of the line sensor 16, and the like, as will be described in detail later. This is an optical filter whose transmission characteristic is designed so that the spectral characteristic (detection intensity for each wavelength) of the reflectance measuring instrument 1 falls within a predetermined range within the range of the measurement wavelength. For example, the luminance of the halogen light source of the light source device 3 has characteristics as shown in FIG. 2 from Planck's radiation law related to black body radiation. In the drawing, luminance distributions corresponding to three types of color temperatures (3100K, 3300K, 3400K) are shown. As can be seen from FIG. 2, the halogen light source has low luminance on the short wavelength side and high luminance on the long wavelength side. In this embodiment, by using the correction filter 5 having a large transmittance on the short wavelength side and a small transmittance on the long wavelength side, variation in detection intensity for each wavelength is reduced.

The operation of this embodiment will be described.
First, the illumination light is irradiated from the light source device 3 without placing the lens W to be examined. The annular light flux 3 a emitted from the light guide 4 passes through the correction filter 5 and is guided to the first pinhole plate 6. In the first pinhole plate 6, only the light that has passed through the first pinhole 6 </ b> A enters the first beam splitter 7. This light behaves like diverging light using the first pinhole 6A as a point light source, collimated by the imaging lens 8, and condensed by the objective lens 10. In this case, since there is no reflector at the condensing position, the reflected light does not enter the spectrometer 13. Therefore, when the output of the line sensor 16 within the predetermined time T is stored in the memory M1 of the controller 18, information on noise (harmful signal component) due to outside light, dark current of the line sensor 16, or the like is obtained.

  Next, a standard sample having a reference surface is placed at the condensing position of the objective lens 10, and the output of the line sensor 16 within a predetermined time T is stored in the memory M2 in the same manner as described above. The light beam emitted from the light source device 3 toward the standard sample is reflected by the reference surface. This reflected light is reflected by the second beam splitter 9 and guided to the first beam splitter 7. In the first beam splitter 7, the light that is folded back toward the second pinhole plate 12 and passes through the second pinhole 12 </ b> A is guided to the spectrometer 13. In the spectroscope 13, the light is reflected by the grating 14 at a reflection angle corresponding to the wavelength, is reflected by the mirror 15, and is received at a predetermined position of the line sensor 16. Since the line sensor 16 is arranged corresponding to the reflection angle for each wavelength in the grating 14, the wavelength is known from the position received on the line sensor 16. Further, the amount of light can be determined from the magnitude of the current generated when the light beam is received. In the second beam splitter 9, a part of the light is transmitted and guided to the observation optical system 11. For this reason, it becomes possible to observe the image of the reference surface with the observation optical system 11, and it is possible to confirm to which position of the reference surface including the focus the illumination light is applied for measurement.

  Further, instead of the standard sample, the test surface W1 of the test lens W is arranged at the condensing position of the objective lens 10, and the output of the line sensor 16 within a predetermined time T is stored in the memory M3. The calculation device C performs predetermined data processing after subtracting the data in the memory M1 from the data in the memories M2 and M3, and calculates the reflection characteristics of the test surface.

Here, the characteristic of the correction filter 5 in this apparatus will be described with a specific example.
For example, when the test lens W is a borosilicate crown glass (BK7) manufactured by Schott Corporation, the spectral characteristics detected by the line sensor 16 of the reflectometer 1 are as shown in FIG. FIG. 3 shows a change in light amount converted from the output of the line sensor 16 for each wavelength in a measurement wavelength region from 380 nm to 780 nm. Such spectral characteristics are obtained by superimposing the characteristics of the respective optical elements on the light emission characteristics of the light source device 3, and the intensity is the lowest in the vicinity of the shortest wavelength of 380 nm (point a) at 580 nm (point b). ) After reaching a peak in the vicinity, it decreases once and then increases again, and the detection intensity is the highest in the vicinity of 680 nm (point c). Further, the detection intensity is lower on the longer wavelength side than the point c. In this spectral characteristic, the detection intensity at point a is lower than that at point c, and the measurement results near point a are likely to be buried in noise, making it difficult to measure the correct reflectance. However, if the exposure time of the line sensor 16 is increased in order to increase the detection intensity near the point a, the vicinity of the point c is saturated and the reflectance near the point c cannot be measured correctly.

  Therefore, the correction filter 5 is designed so that the light amount at the point a having the lowest detection intensity is 1% or more with respect to the light amount at the point c having the highest detection intensity. The transmission characteristics of the correction filter 5 in this case are shown in FIG. The correction filter 5 has high transmittance on the short wavelength side and long wavelength side, and has low transmittance near the wavelength corresponding to the point c. Further, the transmittance in the vicinity of the wavelength corresponding to the point b is set to be low. This is because the amount of light at the point b does not protrude because the point b rises relatively depending on the amount of attenuation at the point c. More specifically, the transmittance of 450 nm or less on the short wavelength side is about 100%, and the transmittance near 700 nm is half or less (about 40%). When such a correction filter 5 is installed in the main body 2, characteristics as shown in FIG. 5 are obtained. The amount of light on the short wavelength side and the long wavelength side is relatively increased and is 1% or more compared to the point c. In addition, the spectral characteristics of the entire wavelength region are adjusted by attenuating the relatively rising region in other wavelength regions. As a result, the spectral characteristics have many portions close to flat, and the difference in detection intensity is small.

  By performing correction with the correction filter 5 as described above, the measurement value of the light amount such as the point c where the light amount was originally large is reduced, so that the output of the line sensor 16 is totally obtained in the same exposure time as when the correction filter 5 is not provided. Becomes smaller. That is, the amount of light in the wavelength region with high transmittance of the correction filter 5 (for example, point a) hardly changes before and after the correction filter 5 is inserted, but the wavelength region with low transmittance of the correction filter 5 (for example, point c). As a result, the amount of data decreases as a whole. For this reason, the exposure time of the line sensor 16 is increased to about 2 to 3 times and adjusted so that a sufficient amount of light can be acquired as a whole.

  According to this embodiment, the correction filter 5 is created according to the characteristics of the reflectometer 1 and the correction filter 5 is arranged on the light source device 3 side of the first beam splitter 7. It is possible to relatively increase the detection intensity in the wavelength region where the output is small. Therefore, it is possible to arrange the intensity distribution of the light quantity within the measurement range including such a wavelength range, and the measurement accuracy can be improved.

Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same component as 1st Embodiment. In addition, overlapping explanation is omitted.
As shown in FIG. 6, the reflectance measuring machine 1 includes a light source device 30 and a main body 2. A spectroscope 13 and an observation optical system 11 are attached to the main body 2. Other configurations except for the configuration of the light source device 30 are the same as those in the first embodiment except that the main body 2 does not have the correction filter 5.

  The light source device 30 includes a halogen light source 31 that is a white light source, a light emitting diode 32 that is a correction unit, a driving device 33 for the light emitting diode 32, and a dichroic mirror 34. The halogen light source 31 and the light emitting diode 32 are disposed at positions that are substantially orthogonal to each other, and the dichroic mirror 34 is disposed at a position where the optical axes intersect each other. As shown in FIG. 7, the light emitting diode 32 is a compensation light source having a peak in the vicinity of 380 nm and a relatively broad emission characteristic. As shown in FIG. 8, the dichroic mirror 34 has a transmittance of about 100 at 400 nm or more, and the transmittance decreases as the wavelength decreases at 400 nm or less, and the transmittance reaches 40% near 380 nm. It has become.

  The operation of this embodiment will be described. Of the light flux emitted from the halogen light source 31 of the light source device 30, about 50% of the light having a wavelength in the vicinity of 380 nm to 400 nm is reflected to the halogen light source 31 side by the transmission characteristics of the dichroic mirror 34, and the remaining light is the light guide. 4 is introduced. At 400 nm or more, about 100% of light is introduced into the light guide 4. On the other hand, the light beam emitted from the light emitting diode 32 is introduced into the light guide 4 after the optical path is bent by 90 ° by the dichroic mirror 34. Therefore, the light flux from the halogen light source 31 and the light flux from the light emitting diode 32 are combined on the incident surface of the light guide 4.

  The light beam introduced into the light guide 4 is emitted as an annular light beam 3a through the light guide 4 and guided to the main body 2. The first pinhole 6A, the first beam splitter 7, the imaging lens 8, the second The light is condensed by the objective lens 10 through the beam splitter 9 and irradiated toward the test surface W1. The reflected light from the test surface W1 is guided to the spectroscope 13 and split. At the time of measurement, measurement is performed in a state where nothing is arranged at the condensing position, a state where the standard sample is disposed, and a state where the lens W is disposed, and the reflectance of the lens W is calculated. The reflectance measuring machine 1 has the spectral characteristics as shown in FIG. 3 only with the halogen light source 31. By additionally using the dichroic mirror 34 and the light emitting diode 32, the reflectance measuring machine 1 has the spectral characteristics as shown in FIG. Modified.

  In this embodiment, the light beam from the halogen light source 31 is originally small on the short wavelength side and further attenuated by the dichroic mirror 34, but before the annular light beam 3 a passes through the first beam splitter 7, the first beam splitter 7 In addition, since the light flux from the light emitting diode 32 disposed on the halogen light source 31 side is added, the light amount on the short wavelength side increases as a whole, so that the intensity distribution of the light amount within the measurement range can be adjusted. Measurement accuracy can be improved.

The present invention can be widely applied without being limited to the above-described embodiments.
For example, the measurement target is not limited to the reflectance. Even when a chromaticity diagram is obtained using reflectance, good measurement accuracy can be obtained.
When expanding the wavelength range for correcting the spectral characteristics, the number of light emitting diodes 32 may be increased, or light emitting diodes 32 having different wavelengths may be added.
Instead of the dichroic mirror 34, a half mirror may be used, or a plurality of reflecting mirrors may be used in combination. Further, using a bifurcated light guide, the halogen light source 31 is disposed on one branched incident surface, the light emitting diode 32 is disposed on the other branched incident surface, and the light beams of the two light sources are combined in the light guide, The intensity distribution of the light quantity of each wavelength within the measurement range may be arranged in the annular luminous flux on the emission side.
The main body 2 and the spectroscope 13 may be configured separately or may be configured integrally.

It is a figure which shows schematic structure of the reflectance measuring machine which concerns on embodiment of this invention. It is a figure which shows the luminance distribution of a halogen light source. It is a figure which shows the spectral characteristic in the state without a correction filter. It is a figure which shows the permeation | transmission characteristic of a correction filter. It is a figure which shows the spectral characteristic in the state which mounted | wore the correction filter. It is a figure which shows schematic structure of a reflectance measuring device. It is a figure which shows the light emission characteristic of a light emitting diode. It is a figure which shows the transmission characteristic of a dichroic mirror. It is a figure which shows the spectral characteristics at the time of using a light emitting diode together.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reflectivity measuring machine 3,30 Light source device 5 Correction filter (correction means, optical filter)
13 Spectrometer 16 Line sensor (light receiving element)
31 White light source 32 Light emitting diode (correction means, compensation light source)
34 Dichroic mirror W1 Test surface

Claims (5)

In a reflectance measuring machine that makes a light beam from a white light source incident on a test surface, and that the reflected light from the test surface is dispersed by a spectroscope and then received by a light receiving element to measure the reflectance of the test surface,
A correction means is provided for reducing variation depending on the wavelength of the detection intensity of the light receiving element when reflected light is detected by the light receiving element between the white light source and the test surface. Reflectivity measuring machine.   The correction means is an optical filter that cuts the amount of light in the wavelength region where the detection intensity is high and corrects the output in the wavelength region where the detection intensity is low to be 1% or more of the output of the region where the detection intensity is high. The reflectance measuring machine according to claim 1, wherein the reflectance measuring machine is provided.   The reflectance measuring machine according to claim 2, wherein the optical filter has a transmittance of 450 nm or less that is twice or more a transmittance near 700 nm.   2. The compensation unit according to claim 1, further comprising: a compensation light source arranged so as to emit a light beam in a wavelength region in which detection intensity is low and to combine the light beam with the light beam from the white light source. Reflectance measuring machine. In a reflectance measurement method in which a light beam from a white light source is incident on a test surface, the reflected light from the test surface is dispersed by a spectroscope and then received by a light receiving element, and the reflectance of the test surface is measured.
Irradiating the surface to be examined after a beam of white light is passed through an optical filter to attenuate the amount of visible light having a wavelength of 500 nm or more;
The reflected light from the test surface is turned back before the optical filter and is incident on the spectroscope;
A reflectance measurement method characterized by comprising:

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